Semiconductor device and method for manufacturing semiconductor device including an electron trap layer

Abstract

A manufacturing method of a semiconductor device in which the threshold voltage is adjusted is provided. The semiconductor device includes a first semiconductor, an electrode electrically connected to the first semiconductor, a gate electrode, and an electron trap layer between the gate electrode and the first semiconductor. By performing heat treatment at higher than or equal to 125° C. and lower than or equal to 450° C. and, at the same time, keeping a potential of the gate electrode higher than a potential of the electrode for 1 second or more, the threshold voltage is increased.

What is claimed is: 
     
       1. A manufacturing method of a semiconductor device comprising:
 forming a first semiconductor; 
 forming a first electron trap layer over the first semiconductor; 
 forming a second electron trap layer over the first electron trap layer; 
 forming a gate electrode over the second electron trap layer; 
 forming an electrode electrically connected to the first semiconductor; and 
 keeping a potential of the gate electrode higher than a potential of the electrode for 1 second or longer at a temperature higher than or equal to 125 ° C. and lower than or equal to 450 ° C., thereby increasing a threshold voltage of the semiconductor device, 
 wherein the second electron trap layer has a higher density of electron trap states than the first electron trap layer. 
 
     
     
       2. The manufacturing method of the semiconductor device according to  claim 1 , wherein the first electron trap layer comprises any one of hafnium oxide, aluminum oxide, and aluminum silicate. 
     
     
       3. The manufacturing method of the semiconductor device according to  claim 1 , wherein the electrode is either a source electrode or a drain electrode. 
     
     
       4. The manufacturing method of the semiconductor device according to  claim 1 ,
 wherein the semiconductor device comprises a second semiconductor and a third semiconductor, 
 wherein the first semiconductor is sandwiched between the second semiconductor and the third semiconductor, and 
 wherein the second semiconductor is provided between the first semiconductor and the electron trap layer. 
 
     
     
       5. The manufacturing method of the semiconductor device, according to  claim 4 , wherein the first semiconductor, the second semiconductor, and the third semiconductor comprise oxide semiconductor. 
     
     
       6. The manufacturing method of the semiconductor device according to  claim 1 , wherein the potential applied to the gate electrode is lower than a highest potential used in the semiconductor device and higher than 1 V. 
     
     
       7. A manufacturing method of a semiconductor device comprising:
 forming a first semiconductor; 
 forming an electron trap layer over the first semiconductor, the electron trap layer comprising a plurality of conductive minute regions; 
 forming a gate electrode over the electron trap layer; 
 forming an electrode electrically connected to the first semiconductor; and 
 keeping a potential of the gate electrode higher than a potential of the electrode for 1 second or longer at a temperature higher than or equal to 125 ° C. and lower than or equal to 450 ° C., thereby increasing a threshold voltage of the semiconductor device, 
 wherein a proportion of the plurality of conductive minute regions in the electron trap layer is smaller than a proportion of a region in the electron trap layer which does not contain the plurality of conductive minute regions. 
 
     
     
       8. The manufacturing method of the semiconductor device according to  claim 7 , wherein the electron trap layer comprises any one of hafnium oxide, aluminum oxide, and aluminum silicate. 
     
     
       9. The manufacturing method of the semiconductor device according to  claim 7 , wherein the electrode is either a source electrode or a drain electrode. 
     
     
       10. The manufacturing method of the semiconductor device according to  claim 7 ,
 wherein the semiconductor device comprises a second semiconductor and a third semiconductor, 
 wherein the first semiconductor is sandwiched between the second semiconductor and the third semiconductor, and 
 wherein the second semiconductor is provided between the first semiconductor and the electron trap layer. 
 
     
     
       11. The manufacturing method of the semiconductor device, according to  claim 10 , wherein the first semiconductor, the second semiconductor, and the third semiconductor comprise oxide semiconductor. 
     
     
       12. The manufacturing method of the semiconductor device according to  claim 7 , wherein the potential applied to the gate electrode is lower than a highest potential used in the semiconductor device and higher than 1 V. 
     
     
       13. A manufacturing method of a semiconductor device comprising:
 forming a first semiconductor layer; 
 forming a second semiconductor layer over the first semiconductor layer; 
 forming a third semiconductor layer over the second semiconductor layer; 
 forming an electron trap layer over the third semiconductor layer; 
 forming a gate electrode over the electron trap layer; and 
 forming an electrode electrically connected to the third semiconductor layer, 
 wherein the electron trap layer comprises a first insulating layer and a second insulating layer that include the same constituent elements and are formed by different formation methods or under different formation conditions, 
 wherein the second insulating layer is provided between the first insulating layer and the gate electrode, and 
 wherein the second insulating layer has a higher density of electron trap states than the first insulating layer. 
 
     
     
       14. The manufacturing method of the semiconductor device according to  claim 13 , wherein a band gap of the first insulating layer is larger than that of the second insulating layer. 
     
     
       15. The manufacturing method of the semiconductor device according to  claim 13 ,
 wherein the first insulating layer is formed by a CVD method. 
 
     
     
       16. The manufacturing method of the semiconductor device according to  claim 13 , wherein electron trap states are contained at an interface between the first insulating layer and the second insulating layer. 
     
     
       17. The manufacturing method of the semiconductor device according to  claim 13 , wherein the electron trap layer is negatively charged. 
     
     
       18. The manufacturing method of the semiconductor device according to  claim 13 , wherein the electron trap layer comprises any one of hafnium oxide, aluminum oxide, and aluminum silicate. 
     
     
       19. The manufacturing method of the semiconductor device according to  claim 13 , wherein the electrode is either a source electrode or a drain electrode. 
     
     
       20. The manufacturing method of the semiconductor device according to  claim 13 , wherein the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer comprise oxide semiconductor.